To begin you'll need to add the spawn helper function to your DayZ server init.c file.
Browse to the mission folder for the map your server is running and open the init.c file.
C:\Program Files (x86)\Steam\steamapps\common\DayZ\Missions\DayZCommunityOfflineMode.Enoch
or
C:\Program Files (x86)\Steam\steamapps\common\DayZServer\mpmissions\dayzOffline.chernarusplus
Add the following text at the very beginning (Before void main) of your init.c file. (Sample Here)
//Spawn helper function
void SpawnObject(string objType, vector objPos, vector objOrientation)
{
Object m_Building = Object.Cast(GetGame().CreateObject(objType, objPos));
if (m_Building == null) return;
m_Building.SetAffectPathgraph(true, false);
GetGame().GetCallQueue(CALL_CATEGORY_SYSTEM).CallLater(GetGame().UpdatePathgraphRegionByObject, 100, false, m_Building);
m_Building.SetPosition(objPos);
m_Building.SetOrientation(objOrientation);
}
You're going to paste the source SpawnObject (From the prefabs page of your choice) below the void main line
Save your file and restart the server